<script>
  function Person(name) {
    this.name = name;
    this.introduce = function() {};
  }
  var p1 = new Person('Jim');
  var p2 = new Person('Alice');
  console.log(p1.introduce == p2.introduce);    // 输出结果：false
</script>

<script>
  function Person() {}                          // 定义函数
  console.log(typeof Person.prototype);         // 输出结果：object
</script>

<script>
  function Person(name) {
    this.name = name;
  }
  Person.prototype.introduce = function() {};
  var p1 = new Person('Jim');
  var p2 = new Person('Alice');
  console.log(p1.introduce);                     // 输出结果：function () {}
  console.log(p1.introduce === p2.introduce);    // 输出结果：true
</script>